Electrostatically focused high power traveling wave tube with spiral electron beam path



w. VElTH ETAL 3,277,332

FOCUSED HIGH POWER TRAVELING WAVE WITH SPIRAL ECTRON BEAM PATH Filed April 23 1963 Get. 4, 1966 ELECTROSTATICALLY TUBE S WW mfiw n Mfey e /0 H rd =2. 92. MU =55 o m 9E4 Fig.1

United States Patent ()fiice 3,277,332 Patented Oct. 4, 1966 s 8 Claims. ((11. 315-35 The invention disclosed herein is concerned wit-h a high power travelling field tube for amplifying ultra high frequencies, with purely electrostatic focusing of the electron beam along a spiral path between an inner and an outer electrode which are wound spirally about the tube axis, whereby the inner electrode is constructed as a delay line which embraces the electron beam at least in par-t and along which an electromagnetic wave is spread with azimuthal delay.

It is already known, in connection with a travelling field tube with a delay line which embraces helically coaxial'ly a cylindrical conductor with circular cross section, to guide an electron beam electrostatically in the space between the delay line and the cylindrical conductor. The cylindrical conductor is for this purpose placed on a direct potential which is higher than that on the delay line. The electrons are along their paths in reciprocal action with a wave on the delay line.

It has also been proposed, in connection with a high power travelling field tube operating according to the principle of the indicated known tube, to guide the electron beam within a hollow delay line structure wound spirally about the tube axis in the space between a metallic structure arranged within the delay line structure, electrically separated therefrom, and the wall par-ts of the delay line structure lying in the direction of the tube axis. The delay line structure is to be of a configuration such that periodic breakthroughs are provided at least in connection with the wall parts facing in the direction of the tube axis. The metallic structure is, as compared with these wall parts of the delay line, placed on a lower direct potential and may be considered as the outer electrode of a cylindrical capacitor, the inner electrode of which is formed by the wall parts of the delay line facing the tube axis. The advantage of such a travelling field tu-be resides in that the high frequency energy is taken in the manner of the magnetron efiect from the potential energy of the electrostatic field.

The outer electrode arranged in the delay line structure influences the high frequency field of the delay line, effecting especially a strong shielding of the high frequency [field from the radiation zone.

The object of the invention is to provide a high power travelling field tube with purely electrostatic focusing of the electron beam, wherein the high frequency field of the delay line is substantially unaffected by the focusing electrodes.

It is for the realization of this object proposed to subdivide the outer electrode of a travelling field tube of the initially indicated kind, into individual periodically successively placed partial electrodes, so as to obtain a periodically electrostatic focusing of the beam in the z direction.

In order to avoid influencing of the high frequency properties of the delay line by the leads conducting the direct voltage to the partial electrodes of the outer electrode, it is in accordance with another feature of the invention proposed to mutually connect by means of short spiral parts respective groups of an identical number of partial electrodes which are electrically directly connected. The spiral parts are to be dimensioned so that the transmission range of the delay line falls in a barrier range of the spiral parts. This measure constitutes a choking of the direct voltage supply leads of the partial electrodes which prevent a feedback coupling of the electromagnetic field over these leads.

It is particularly advantageous to provide a shielding body forming a helical surface with the turns thereof arranged in known manner between the respective inner and outer electrodes, in order to avoid mutual influencing of the high frequency fields of the delay line in longitudinal direction of the tube. The shielding body can thereby additionally serve for securing the inner and outer electrodes, it being understood, of course, that the outer electrode must be electrically insulated with respect to the shielding body. However, it is also possible to secure the inner and outer electrode on a separate web or brace which extends spirally within the space between the helical turns of the shielding body.

Further details and features of the invention will appear in the course of the description which is rendered below with reference to the accompanying drawing, wherein parts which are unnecessary for the understanding of the invention have been omitted and wherein corresponding parts are identically referenced.

FIG. 1 shows the amplifier part of a travelling field tube according to the invention;

FIG. 2 represents on a larger scale a section A of FIG. 1;

FIG. 3 indicates the manner of focusing the electron beam;

FIG. 4 illustrates in schematic manner how the direct voltage is conducted to the partial electrodes; and

FIG. 5 shows the use of a special web or brace for securing the delay line and the partial electrodes of the outer electrode.

As noted above, FIG. 1 shows the amplification part of a travelling field tube according to the invention, FIG. 2 representing the section A of FIG. 1 to bring out details more clearly. Numeral 1 indicates a ribbon-shaped electron beam which is guided along a spiral path about the tube axis z in the space between a delay line (inner electrode) formed by hook-like metal parts 2 and an outer electrode formed of individual periodically successive partial electrodes 3. The partial electrodes 3 form U- sh-aped metal webs facing the tube envelope (not shown) and arranged in intermittent sequence with respect to the metal webs 2 of the delay line. A helical shielding member 4 is provided for shielding the high frequency field of the delay line in the z direction, such shielding member also serving for securing the delay line. The hooklike metal webs 2 are uniformly distributed over the circumference of the helical member and are soldered there to. The partial electrodes 3 of the outer electrode which may be secured on the shielding body in insulated relation with respect thereto, are, as compared with the metal webs 2 and the shielding member 4, on a lower direct.

potential. The two electrode systems comprising the metal webs 2 and the partial electrodes 3, form a chain of individual electrostatic lenses, through which the electron beam 1 is guided, as shown in FIG. 3, in the manner of a periodic electrostatic focusing. The high frequency field of the delay line formed by the hook-like metal webs 2, is by the partial electrodes only very slightly affected.

FIG. 4 shows in schematic manner the direct voltage leads for the partial electrodes 3 of the outer electrode. The partial electrodes receive a common negative bias over the line 5. Two respective partial electrodes 3 which are electrically directly connected, form a group which is connected with the next following group by way of a short helical member 6. The helices 6, which are to be dimensioned so that the transmission range of the tube falls within the barrier rangethereof, effect a choking of the direct voltage lead 5, thus preventing influencing of the high frequency properties of the delay line, for example, by feedback of the direct voltage lead 5.

The delay line and/ or the partial electrodes of the outer electrode, need not necessarily be secured on the helical shielding member; they may be secured, as shown in FIG. 5, on a separate brace 7 which extends along the space between the helix parts of the shielding member 4.

The invention is not inherently limited to the described and illustrated examples. It is, for example, possible to use a helical line as a delay line. Such helical line may be advantageously secured on the brace 7 FIG. The cooling of a travelling field tube according to the invention is advantageously effected by using a metallic vacuum envelope which can be soldered to the shielding member 4 and directly cooled by convection.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

We claim:

1. A high power travelling field tube, especially for amplifying very high frequencies, with purely electrostatic focusing of the electron beam which is guided along a spiral path within the space of an inner and an outer electrode, which electrodes are jointly spirally disposed about the tube axis, said inner electrode being formed as a delay line which embraces the electron beam at least in part and along which an electromagnetic wave is spread with azimuthal delay, said outer electrode being subdivided into individual periodic-ally successively disposed partial electrodes.

-2. A travelling field tube according to claim 1, comprising a plurality of groups of partial electrodes, each group having the same number of partial electrodes, means for electrically interconnecting the partial electrodes of each group, and helical members for connecting the re.- spective groups.

3. A travelling field tube according to claim 2, wherein each group comprises two partial electrodes.

4. A travelling field tube according to claim 1, comprising a metallic 'helicall'y extending shielding body, said inner and outer electrodes being disposed between the turns of said shielding body.

5. A travelling field tube according to claim 4, wherein said inner and outer electrodes are secured on said helical shielding body.

6. A travelling field tube according to claim 5, wherein said inner electrode comprises hook-shaped metal webs which are secured at the rim of the helical shielding body.

7. A travelling field tube according to claim 6, wherein the outer and the inner electrode are respectively formed of a plurality of metal webs, forming partial electrodes, the partial electrodes of the outer electrode forming U- shaped metal webs facing the envelope of the tube and being arranged in intermittent sequence with respect to the webs of the inner electrode.

8. A travelling field tube according to claim 4, comprising a separate brace extending spirally along the space between the turns of said shielding member, at least parts of one of said electrodes being secured on said brace.

References Cited by the Examiner UNITED STATES PATENTS 2,806,177 9/1957 Haefi 3153.5 X 2,900,558 8/1959 Watkins 315-393 X 3,099,766 7/1963 Veith et al 315-4 93 X HERMAN KARL SAADBACH, Primary Examiner.

R. D. OOHN, Assistant Examiner. 

1. A HIGH POWER TRAVELLING FIELD TUBE, ESPECIALLY FOR AMPLIFYING VERY HIGH FREQUENCIES, WITH PURELY ELECTROSTATIC FOCUSING OF THE ELECTRON BEAM WHICH IS GUIDED ALONG A SPIRAL PATH WITHIN THE SPACE OF AN INNER AND AN OUTER ELECTRODE, WHICH ELECTRODES ARE JOINTLY SPIRALLY DISPOSED ABOUT THE TUBE AXIS, SAID INNE RELECTRODE BEING FORMED AS A DELAY LINE WHICH EMBRACES THE ELECTRON BEAM AT LEAST IN PATH AND ALONG WHICH AN ELECTROMAGNETIC WAVE IS SPREAD WITH AZIMUTHAL DELAY, SAID OUTER ELECTRODE BEING SUBDIVIDED INTO INDIVIDUAL PERIODICALLY SUCCESSVIELY DISPOSED PARTIAL ELECTRODES. 